This application relates to a device for driving an axle and, in particular, to hydrostatic transaxles intended for use in vehicles and similar applications.
Hydrostatic transaxles generally comprise a transmission disposed in a sump and driving an output axle or axles. Such transaxles often include a sump vent in communication with atmosphere or have an added external fluid expansion tank or reservoir to accommodate sump fluid expansion and contraction within a broad range of operating conditions and temperatures. An external fluid expansion tank or reservoir can be damaged by impact and weathering and may develop leaks in associated hoses, tubes, fittings, connections and the like. A sump vent may leak sump fluid during handling, installation or under certain transaxle operating conditions and may allow entry of moisture or other contaminants into the sump fluid which can cause damage to mechanical components running inside the transaxle housing. External components require additional space and material and limit vehicle configuration versatility. An internal bellows may be used but such known designs require sufficient space within the transaxle housing and increase the required size of the housing. For the foregoing reasons, there is a need for a fluid expansion means and a sealed sump fully contained within a transaxle case or housing which efficiently and cost-effectively utilize space and material.